Radioactive nuclides are used in various fields of technology and science, as well as for medical purposes. These radionuclides are produced in research reactors or cyclotrons. However, since the number of facilities for commercial production of radionuclides is limited already and expected to decrease, it is desired to provide alternative production sites.
The neutron flux density in the core of a commercial nuclear reactor is measured, inter alia, by introducing solid spherical probes into instrumentation tubes passing through the reactor core. It was therefore suggested that instrumentation tubes of commercial nuclear reactors shall be used for producing radionuclides when the reactor is in power generating operation. In particular, one or more instrumentation tubes of an aero-ball measuring system of a commercial nuclear reactor can be used, and existing components of the ball measuring system can be modified and/or supplemented to enable an effective production of radionuclides during reactor operation.
EP 2 093 773 A2 suggests that existing instrumentation tubes conventionally used for housing neutron detectors may be used to generate radionuclides during normal operation of a commercial nuclear reactor. In particular, spherical irradiation targets are linearly pushed into and removed from the instrumentation tubes. Based on the axial neutron flux profile of the reactor core, the optimum position and exposure time of the targets in the reactor core are determined. A driving gear system is used for moving and holding the irradiation targets in the instrumentation tubes.
US 2013/0177118 A1 discloses a system that allows irradiation targets to be irradiated in a nuclear reactor and deposited in a harvestable configuration without direct human interaction or discontinuation of power-producing activities. The system includes accessible end-points that store desired produced isotopes for handling and/or shipping. A penetration pathway can provide access through an access barrier in the reactor containment and to an instrumentation tube in the reactor vessel. The system further comprises a diverter, a driving mechanism, an indexer and a harvesting cask which can all be located inside of a containment building in the nuclear plant. A Cask tube provides a pathway for irradiation targets to pass out of a diverter and may include one or more counters that detect an exact number, amount, or activity of activated irradiation targets that exit through the cask tube. An exhaust line is connected to the cask tube which allows a pneumatic fluid used to drive irradiation targets to safely exit the system. The cask tube may be used with multiple storage casks based on target properties. One or more stops may be inserted into the cask tube at desired positions to separate out a certain population of irradiation targets.
US 2013/0177125 A1 is directed to a system for managing irradiation targets and instrumentation access to a nuclear reactor, the system comprising: a penetration pathway connecting an origin point outside an access barrier of the nuclear reactor to an instrumentation tube extending into the nuclear reactor inside the access barrier, wherein the penetration pathway is traversable by at least one irradiation target, wherein the penetration pathway includes one of at least one instrumentation path and at least one irradiation target path distinct from the instrumentation path, and at least one shared path; and a selector configured to connect only one of the instrumentation path and the irradiation target path to the shared path so as to form the penetration pathway. The selector includes a selection block coupled to at least one motor and provides several different pathways, depending on its position. Based on the vertical positioning of selection block, only one of the instrumentation path and the irradiation target path may align with, and open into, shared pathway headed toward an instrumentation tube.
US 2013/0170927 A1 discloses apparatuses and methods for producing radioisotopes in instrumentation tubes of operating commercial nuclear reactors. Irradiation targets are inserted and removed from instrumentation tubes during operation and converted to radioisotopes. A harvesting cask and/or a cask tube can be equipped with a target counter that counts or measures properties of irradiation targets moving into the harvesting cask. The irradiation targets may further include a tracking target located at a known position among all other targets that is fabricated of a material that is different from all other targets and permits tracking or locating of the irradiation targets. Several combinations of forks, dividers, turntables and sorters may be used to create unique loading and harvesting paths for the irradiation targets.
US 2013/0315361 A1 also relates to an apparatus and methods for producing radioisotopes in multiple instrumentation tubes of operating commercial nuclear reactors. Irradiation targets are inserted and removed from multiple instrumentation tubes and converted to radioisotopes during operation of the nuclear reactor. An indexer is provided to selectively direct irradiation targets to one of the multiple instrumentation tubes within nuclear reactor by making accessible a penetration pathway leading to the individual instrumentation tube. The indexer may further selectively allow irradiation targets from multiple instrumentation tubes to enter into a single/combined penetration pathway leading to harvesting points outside of an access barrier. Positioning irradiation targets are provided to properly position other irradiation targets at desired positions within or near the nuclear core. The positioning targets can be made of an inexpensive inert material or of a magnetic material, and may be held in the instrumentation tube by means of a magnetic latch. After irradiation, the targets are delivered from the instrumentation tube into a harvesting cask, and the positioning targets may be sorted out from the harvesting cask due to their markings or physical properties.
Conventional aero-ball measuring systems are known in the art and disclosed, for example, in GB 1 324 380 A and U.S. Pat. No. 3,263,081 A.
The above radionuclide generation systems require structures for processing activated irradiation targets which are permanently installed in the reactor facilities. However, installing such permanent radionuclide generation systems will involve high costs. In addition, the systems may require that one or more specific instrumentation tubes are selected for radionuclide generation. These instrumentation tubes will no longer be available for in-core measurement of neutron flux or other reactor conditions. Moreover, neutron flux in the reactor core will vary depending on reactor load and operating conditions. Therefore, the neutron flux at the specific instrumentation tube selected for radionuclide generation may be insufficient resulting in high downtimes, or radionuclide generation may require extended process times.
Further, due to the high activity of the activated irradiation targets retrieved from the instrumentation tubes, and since space within the reactor containment is limited, the targets are difficult to process. In particular, the activated targets including the radioactive nuclides must be filled into and stored in containers provided with heavy radiation shielding. However, the chambers for the Traversing Incore Probe (TIP) system and/or aero-ball measuring system do not have any structures for packaging and transporting those heavy containers. Provision of additional water locks in the reactor containment for handling of the activated targets and shielded containers would also be too expensive.